Without describing basic WLAN forwarding, OpenFlow, or SDN, I’m going to jump in and start discussing HREAP and close with questions and thoughts pertaining to protocols of choice for achieving a “controller based network.” 

For those that aren’t familiar with Cisco HREAP, it is a design for Wireless LANs in which only control traffic gets tunneled back to the controller and the data traffic stays local on the switch.  The IEEE protocol used to communicate between an AP and a controller is called CAPWAP. There are various use cases for the technology, not described here, but that is the 100,000 foot overview.

So, looking at the diagram below, we see a very basic implementation of HREAP. 

After reading Ivan Pepelnjak’s (ipspace) and Martin Casado’s (networkheresy) blogs recently, I noticed they were making general comparisons on network tunneling protocols.  These protocols are nothing new, for example using UDP, GRE, EoMPLS, VPLS, and a new one being mentioned over the past several months, VXLAN.  However, what caught my attention was CAPWAP was also a protocol each of them used to compare to GRE, UDP, and VXLAN.  As you’ll recall in my recent OpenFlow post, I spent quite a bit of time comparing OpenFlow to CAPWAP in the sense OpenFlow is being used to separate the control and data planes on switches and CAPWAP is being used to separate the control and data planes on Access Points.

I figured, why not, let’s google CAPWAP and OpenFlow together and see what comes up.  No surprise, you see the post from Matt Davy at IU who was drawing a similar comparison to OF/SDN to CAPWAP/WLAN, my recent blog, Ivan’s blog, Martin’s blog, and then finally the reason why I’m writing this – I saw a link to openvswitch.org that talked about building support for CAPWAP into the open vswitch.  Interesting, right?  Well, to me it is!  So after digging further, it looks like Jesse Gross (from Nicira, the company who does much of the development work on open vswitch) had some comments in the commit log for this feature.